Re: [PATCH 2/2] ARM: dts: imx6qdl: tqma6: minor fixes

[Matthias Schiffer]

On Wed, 2020-08-26 at 10:49 -0300, Fabio Estevam wrote:
> On Wed, Aug 26, 2020 at 10:13 AM Matthias Schiffer
> <matthias.schiffer@xxxxxxxxxxxxxxx> wrote:
> 
> > Using GPIOs for chipselect would require different pinmuxing. Also,
> > why
> > use GPIOs, when the SPI controller has this built in?
> 
> In the initial chips with the ECSPI controller there was a bug with
> the native chipselect controller and we had to use GPIO.

Ah, I see.

Nevertheless, hardware that uses the native chipselects of newer chips
exists (for example our TQ-Systems starterkit mainboards, the DTS of
which we're currently preparing for mainline submission). Shouldn't
num-cs be set for boards (or SoM DTSI) where not all CS pins of the SoC
are usable?

In any case, my original question was about the intended logic for
num_chipselects for SPI drivers. My proposal was:

- If num-cs is set, use that
- If num-cs is unset, use the number of cs-gpios
- If num-cs is unset and no cs-gpios are defined, use a driver-provided 
default

How do other SPI controller drivers deal with this?